148 MODERN METHODS OF TESTING MILK 



Leach's test, which is more delicate, is performed 

 as follows: Make a solution of hydrochloric acid (spe- 

 cific gravity 1.2) containing 2 cc. of 10 per cent, ferric 

 chloride per liter. Add 10 cc. of this solution to 10 

 cc. of milk in a white teacup and heat slowly over a 

 flame to boiling, giving the cup a rotary motion. If 

 formalin is present, a violet coloration appears, vary- 

 ing in depth with the amount present. 



Test for borax and boric acid. To 25 cc. of milk 

 add lime water, until the milk is alkaline, evaporate to 

 dryness and burn to an ash in a small porcelain or 

 platinum dish. To the ash add a few drops of dilute 

 hydrochloric acid, not too much; then add a few drops 

 of water and place in this water solution a strip of 

 turmeric-paper (obtainable at drug-stores). Then dry 

 the paper, when a cherry-red color will appear on the 

 paper if either borax or boric acid is present. This test 

 is made still more certain by moistening the reddened 

 paper with a drop of an alkali solution, when the pa- 

 per turns to a dark-olive color in the presence of borax 

 or boric acid. 



Test for sodium carbonate. To 10 cc. of milk add 

 10 cc. of alcohol and a few drops of a I per cent, so- 

 lution of rosolic acid. Carbonates are present if a 

 rose-red color appears, while pure milk shows a brown- 

 ish-yellow color. 



ADULTERATIONS OF CREAM 



The adulterants of cream are the same as those for 

 milk and are detected in the same manner. Gelatine 

 and sucrate of lime are used to some extent to give 

 cream a greater consistency. 



